The Research Of Variable-line-space Gratings With Double Frequency

In order to improve the accuracy of the grating sensor in the field of microdisplacement,a mirror reading system based on variable-pitch grating(also called double-frequency reading system)is proposed.This system uses the main grating and its image to generate the moore fringe signal,which can be obtained without gaps.Moore fringe signal can be doubled signal output,can improve the sensitivity.When the light emitted by the light source through the moore parallel to the focus after the incident lens,the focus of light through the aperture,the collimator lens perpendicular to the incident on the grating,the beam diffraction in the grating,the detector to receive a fixed angle diffraction.The detected signals are analyzed and processed by a spectrometer.1.The grating used in the test is a grating structure designed by ourselves.Compared with the original equidistant grating,it has the advantages of automatic focusing,aberration adjustment and distortion.The grating used has two different theoretical derivation processes,two different structures,one grating with fixed duty cycle,which is deduced by means of Fourier transform;the other is that the duty cycle is not for the fixed grating structure,the spatial superposition method is used to deduce.2.According to the different light sources,the spherical light and plane light are used to detect the unused optical path.The plane optical detection optical path and the spherical optical detection optical path are designed correspondingly.3.Finally,using the hypothesis test method,assuming a certain light transmission function,into the process of derivation,the data processing,the data obtained and the theoretical value of contrast.